8 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Auburn | 1 | 14,215 | 13,537 | 0.8% | 1,630 | 9 | City |
| Garrett | 2 | 6,720 | 6,548 | 0.43% | 1,613 | 4 | City |
| Butler | 3 | 2,689 | 2,628 | 0.37% | 1,325 | 2 | City |
| Waterloo | 4 | 2,179 | 2,112 | 0.51% | 1,033 | 2 | Town |
| Ashley | 5 | 1,048 | 1,027 | 0.38% | 550 | 2 | Town |
| St. Joe | 6 | 420 | 410 | 0.48% | 1,254 | 0 | Town |
| Corunna | 7 | 240 | 236 | 0.42% | 1,341 | 0 | Town |
| Altona | 8 | 221 | 215 | 0.45% | 1,089 | 0 | Town |
Auburn is the largest city in DeKalb County, with a population of 14,215.
Altona is the smallest city in DeKalb County, with a population of 221.
There are 8 cities in DeKalb County, Indiana.